ABSTRACT
Castration-resistant prostate cancer (CRPC) is defined by resistance of the tumor to androgen deprivation therapy (ADT). Several molecular changes, particularly in the AR signaling cascade, have been described that may explain ADT resistance. The variety of changes may also explain why the response to novel therapies varies between patients. Testing the specific molecular changes may be a major step towards personalized treatment of CRPC patients. The aim of our study was to evaluate the molecular changes in the AR signaling cascade in CRPC patients. We have developed and validated several methods which are easy to use, and require little tissue material, for exploring AR signaling pathway changes simultaneously. We found that the AR signaling pathway is still active in the majority of our CRPC patients, due to molecular changes in AR signaling components. There was heterogeneity in the molecular changes observed, but we could classify the patients into 4 major subgroups which are: AR mutation, AR amplification, active intratumoral steroidogenesis, and combination of AR amplification and active intratumoral steroidogenesis. We suggest characterizing the AR signaling pathway in CRPC patients before beginning any new treatment, and a recent fresh tissue sample from the prostate or a metastatic site should be obtained for the purpose of this characterization.
ABSTRACT
PURPOSE: Dihydrotestosterone is the main active androgen in the prostate and it has a role in prostate cancer progression. After androgen deprivation therapy androgen receptor signaling is still active in tumor cells. Persistent intratumor steroidogenesis and androgen receptor changes are responsible for this continued activity, which influences the efficacy of prostate cancer treatment. We hypothesized that combining a 5α-reductase inhibitor and an antiandrogen would block intratumor androgen synthesis and androgen receptor protein activity. Thus, it would act synergistically to reduce tumor cell proliferation. MATERIALS AND METHODS: The expression level of 5α-reductase and androgen receptor in endocrine therapy naïve prostate cancer and castration resistant prostate cancer tissues, and cell line models was determined by microarray and quantitative polymerase chain reaction analysis. Intracellular androgen was measured with radioimmunoassay. Tumor cell proliferation was determined using coloric MTT assay. The synergistic effects of combination treatments on tumor cell proliferation were calculated using the Chou-Talalay equation. RESULTS: In all prostate cancer cases 5α-reductase-1 and 3 were up-regulated. Androgen receptor was up-regulated in metastatic prostate cancer and castration resistant prostate cancer cases. The 5α-reductase inhibitor dutasteride effectively decreased dihydrotestosterone production in prostate cancer and castration resistant prostate cancer cell lines. Furthermore, dutasteride combined with the novel antiandrogen enzalutamide synergistically suppressed endocrine therapy naïve prostate cancer and castration resistant prostate cancer cell proliferation. CONCLUSIONS: In this study the combination of a 5α-reductase inhibitor and (novel) antiandrogens synergistically inhibited tumor cell proliferation. These findings support clinical studies of combinations of a 5α-reductase inhibitor and (novel) antiandrogens as first line treatment of prostate cancer and castration resistant prostate cancer.
Subject(s)
5-alpha Reductase Inhibitors/pharmacology , Azasteroids/pharmacology , Cell Proliferation/drug effects , Phenylthiohydantoin/analogs & derivatives , Prostatic Neoplasms, Castration-Resistant/pathology , Prostatic Neoplasms/pathology , Benzamides , Drug Synergism , Drug Therapy, Combination , Dutasteride , Humans , Male , Nitriles , Phenylthiohydantoin/pharmacology , Tumor Cells, CulturedABSTRACT
Current endocrine treatment for advanced prostate cancer does not result in a complete ablation of adrenal androgens. Adrenal androgens can be metabolized by prostate cancer cells, which is one of the mechanisms associated with progression to castration-resistant prostate cancer (CRPC). Aldo-keto reductase family 1 member C3 (AKR1C3) is a steroidogenic enzyme that plays a crucial role in the conversion of adrenal androgen dehydroepiandrosterone (DHEA) into high-affinity ligands for the androgen receptor (testosterone [T] and dihydrotestosterone [DHT]). The aim of this study was to examine whether AKR1C3 could be used as a marker and therapeutic target for CRPC. AKR1C3 mRNA and protein levels were upregulated in CRPC tissue, compared with benign prostate and primary prostate cancer tissue. High AKR1C3 levels were found only in a subset of CRPC patients. AKR1C3 can be used as a biomarker for active intratumoral steroidogenesis and can be measured in biopsy or transurethral resection of the prostate specimens. DuCaP (a CRPC cell line that has high AKR1C3 expression levels) used and converted DHEA under hormone-depleted conditions into T and DHT. The DHEA-induced growth of DuCaP could be antagonized by indomethacine, an inhibitor of AKR1C3. This study indicates that AKR1C3 can be considered a therapeutic target in a subgroup of patients with high AKR1C3 expression.
Subject(s)
3-Hydroxysteroid Dehydrogenases/metabolism , Biomarkers, Tumor/metabolism , Hydroxyprostaglandin Dehydrogenases/metabolism , Molecular Targeted Therapy , Orchiectomy , Prostatic Neoplasms/enzymology , Prostatic Neoplasms/surgery , Aldo-Keto Reductase Family 1 Member C3 , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Dehydroepiandrosterone/pharmacology , Dihydrotestosterone/metabolism , Humans , Indomethacin/pharmacology , Male , Prostatic Neoplasms/pathology , Testosterone/metabolismABSTRACT
Considerable levels of testosterone and dihydrotestosterone (DHT) are found in prostate cancer (PCa) tissue after androgen deprivation therapy. Treatment of surviving cancer-initiating cells and the ability to metabolize steroids from precursors may be the keystones for the appearance of recurrent tumors. To study this hypothesis, we assessed the expression of several steroidogenic enzymes and stem cell markers in clinical PCa samples and cell cultures during androgen depletion. Gene expression profiles were determined by microarray or qRT-PCR. In addition, we measured cell viability and analyzed stem cell marker expression in DuCaP cells by immunocytochemistry. Seventy patient samples from different stages of PCa, and the PCa cell line DuCaP were included in this study. The androgen receptor (AR) and enzymes (AKR1C3, HSD17B2, HSD17B3, UGT2B15 and UGT2B17 ) that are involved in the metabolism of adrenal steroids were upregulated in castration resistant prostate cancer (CRPC). In vitro, some DuCaP cells survived androgen depletion, and eventually gave rise to a culture adapted to these conditions. During and after this transition, most of the steroidogenic enzymes were upregulated. These cells also are enriched with stem/progenitor cell markers cytokeratin 5 (CK5) and ATP-binding cassette sub-family G member 2 (ABCG2). Similarly, putative stem/progenitor cell markers CK5, c-Kit, nestin, CD44, c-met, ALDH1A1, α2-integrin, CD133, ABCG2, CXCR4 and POU5F1 were upregulated in clinical CRPC. The upregulation of steroidogenic enzymes and stem cell markers in recurrent tumors suggests that cancer initiating cells can expand by adaptation to their T/DHT deprived environment. Therapies targeting the metabolism of adrenal steroids by the tumor may prove effective in preventing tumor regrowth.
